End effector identification by mechanical features

ABSTRACT

According to one aspect of the present disclosure, a surgical instrument is disclosed. The instrument includes a handle portion, a body portion extending distally from the handle portion and defining a first longitudinal axis and a loading unit. The loading unit includes a tool assembly, the loading adapted to be coupled to the body portion. The instrument also includes a sensor tube movably positioned within the body portion, the sensor tube adapted to engage the loading unit and a load switch coupled to a microcontroller. The load switch is adapted to be actuated by the sensor tube when the sensor tube is engaged by the loading unit being inserted into the body portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of and priority to U.S.Provisional Application Ser. No. 61/225,377 filed on Jul. 14, 2009,which is a continuation in part application of U.S. application Ser. No.12/345,167 filed on Dec. 28, 2008, which is a continuation applicationof U.S. application Ser. No. 11/544,203 filed on Oct. 6, 2006, issued asU.S. Pat. No. 7,481,348, and of U.S. application Ser. No. 12/189,834filed on Aug. 12, 2008, which claims priority to a U.S. ProvisionalApplication Ser. No. 60/997,854 filed on Oct. 5, 2007, the entirecontents of all of which are hereby incorporated by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates to a surgical instrument adapted to becoupled to removable loading units having various end effectors. Moreparticularly, the present disclosure relates to a surgical instrumentwhich includes a mechanism for identifying the type of an end effectormounted to the loading unit.

2. Background of Related Art

Surgical instruments which include a tool assembly mounted on a distalend of a body portion of the surgical instrument for articulation arewell known. Typically, such surgical instruments include articulationcontrol mechanisms which allow an operator to remotely articulate thetool assembly in relation to the body portion of a surgical instrumentto allow the operator to more easily access, operate on, and/ormanipulate tissue.

Such articulating tool assemblies have become desirable, especially inthe endoscopic surgical procedures. In an endoscopic surgical procedure,the distal end of a surgical instrument is inserted through a smallincision in the body to access a surgical site. Typically, anappropriately sized cannula, e.g., 5 mm, 10 mm, etc., is insertedthrough the body incision to provide a guide channel for accessing thesurgical site.

Current known devices can typically require 10-60 pounds of manual handforce to clamp tissue and deploy and form surgical fasteners in tissuewhich, over repeated use, can cause a surgeon's hand to become fatigued.Gas powered pneumatic staplers which implant surgical fasteners intotissue are known in the art. Certain of these instruments utilize apressurized gas supply which connects to a trigger mechanism. Thetrigger mechanism, when depressed, simply releases pressurized gas toimplant a fastener into tissue.

Motor-powered surgical staplers are also known in the art. These includepowered surgical staplers having motors which activate staple firingmechanisms. However, these motor powered devices only provide forlimited user control of the stapling process. The user can only toggle asingle switch and/or button to actuate the motor and appliescorresponding torque to the stapler's firing mechanisms. In certainother devices, a controller is used to control the stapler.

There is a continual need for new and improved powered surgical staplerswhich include various sensors. The sensors provide relevant feedback tofeedback controllers which automatically adjust various parameters ofthe powered stapler in response to sensed feedback signalsrepresentative of stapler operation, including articulation andactuation of the tool assemblies.

SUMMARY

According to one aspect of the present disclosure, a surgical instrumentis disclosed. The instrument includes a handle portion, a body portionextending distally from the handle portion and defining a firstlongitudinal axis and a loading unit. The loading unit includes a toolassembly, the loading adapted to be coupled to the body portion. Theinstrument also includes a sensor tube movably positioned within thebody portion, the sensor tube adapted to engage the loading unit and aload switch coupled to a microcontroller. The load switch is adapted tobe actuated by the sensor tube when the sensor tube is engaged by theloading unit being inserted into the body portion.

According to another aspect of the present disclosure, a surgicalinstrument is disclosed. The instrument includes a handle portion and abody portion extending distally from the handle portion and defining afirst longitudinal axis. The body portion includes a distal end adaptedto releasably engage both articulating and non-articulating loading unittypes. The instrument also includes an articulation mechanism configuredto articulate an articulating tool assembly coupled to an articulatingloading unit and a sensor tube movably positioned within the bodyportion. The sensor tube is adapted to engage the articulating loadingunit. The instrument further includes a load switch coupled to amicrocontroller and adapted to be actuated by the sensor tube when thesensor tube is engaged by the articulating loading unit, wherein uponactuation the load switch signals the microprocessor to activate thearticulation mechanism.

According to a further embodiment of the present disclosure a surgicalinstrument is disclosed. The instrument includes a handle portion and abody portion extending distally from the handle portion and defining afirst longitudinal axis. The body portion includes a distal end adaptedto releasably engage a plurality of loading unit types. The instrumentalso includes a sensor tube movably positioned within the body portion,the sensor tube adapted to engage each of the plurality of loading unittypes and to move a predetermined distance in response thereto; and avariable loading unit sensor adapted to determine a type of a loadingunit engaged with the body portion based on the predetermined distancethe sensor tube has been displaced.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the subject instrument are described herein withreference to the drawings wherein:

FIG. 1 is a perspective view of a powered surgical instrument accordingto an embodiment of the present disclosure;

FIG. 2 is a partial enlarged perspective view of the powered surgicalinstrument of FIG. 1 according to the embodiment of the presentdisclosure;

FIG. 3 is a partial enlarged plan view of the powered surgicalinstrument of FIG. 1 according to the embodiment of the presentdisclosure;

FIG. 4 is a partial sectional view of internal components of the poweredsurgical instrument of FIG. 1 in accordance with an embodiment of thepresent disclosure;

FIG. 5 is a perspective view of a loading unit according to oneembodiment of the present disclosure;

FIG. 6 is a partial sectional view of internal components of the loadingunit and the powered surgical instrument of FIG. 1 according to theembodiment of the present disclosure;

FIG. 7 is a partial sectional view of internal components of the loadingunit and the powered surgical instrument of FIG. 1 according to theembodiment of the present disclosure; and

FIG. 8 is a partial perspective sectional view of variable loading unitsensor according to the embodiment of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the presently disclosed powered surgical instrument arenow described in detail with reference to the drawings, in which likereference numerals designate identical or corresponding elements in eachof the several views. As used herein the term “distal” refers to thatportion of the powered surgical instrument, or component thereof,farther from the user while the term “proximal” refers to that portionof the powered surgical instrument or component thereof, closer to theuser.

A powered surgical instrument, e.g., a surgical stapler, in accordancewith the present disclosure is referred to in the figures as referencenumeral 10. Referring initially to FIG. 1, powered surgical instrument10 includes a housing 110, an endoscopic portion 140 defining a firstlongitudinal axis A-A extending therethrough, and an articulating toolassembly (e.g., end effector 160), defining a second longitudinal axisB-B extending therethrough. Endoscopic portion 140 extends distally fromhousing 110 and the end effector 160 is disposed adjacent a distalportion of endoscopic portion 140. In an embodiment, the components ofthe housing 110 are sealed against infiltration of particulate and/orfluid contamination and help prevent damage of the components bysterilization processes.

According to an embodiment of the present disclosure, end effector 160includes a first jaw member having one or more surgical fasteners (e.g.,cartridge assembly 164) and a second opposing jaw member including ananvil portion for deploying and forming the surgical fasteners (e.g., ananvil assembly 162). In certain embodiments, the staples are housed incartridge assembly 164 to apply linear rows of staples to body tissueeither in simultaneous or sequential manner. Either one or both of theanvil assembly 162 and the cartridge assembly 164 are movable inrelation to one another between an open position, in which the anvilassembly 162 is spaced from cartridge assembly 164, and an approximatedor clamped position, in which the anvil assembly 162 is in juxtaposedalignment with cartridge assembly 164.

It is further envisioned that end effector 160 is attached to a mountingportion 166, which is pivotably attached to a body portion 168. Bodyportion 168 may be integral with endoscopic portion 140 of poweredsurgical instrument 10, or may be removably attached to the instrument10 to provide a replaceable, disposable loading unit (DLU) or single useloading unit (SULU) (e.g., loading unit 169). In certain embodiments,the reusable portion may be configured for sterilization and re-use in asubsequent surgical procedure.

The loading unit 169 may be connectable to endoscopic portion 140through a bayonet connection. It is envisioned that the loading unit 169has an articulation link connected to mounting portion 166 of theloading unit 169 and the articulation link is connected to a linkage rodso that the end effector 160 is articulated as the linkage rod istranslated in the distal-proximal direction along first longitudinalaxis A-A as discussed in more detail below. Other means of connectingend effector 160 to endoscopic portion 140 to allow articulation may beused, such as a flexible tube or a tube comprising a plurality ofpivotable members.

The loading unit 169 may incorporate or be configured to incorporatevarious end effectors, such as vessel sealing devices, linear staplingdevices, circular stapling devices, cutters, graspers, etc. Such endeffectors may be coupled to endoscopic portion 140 of powered surgicalinstrument 10. An intermediate flexible shaft may be included betweenhandle portion 112 and loading unit. It is envisioned that theincorporation of a flexible shaft may facilitate access to and/or withincertain areas of the body.

With reference to FIGS. 1 and 2, an enlarged view of the housing 110 isillustrated according to an embodiment of the present disclosure. In theillustrated embodiment, housing 110 includes a handle portion 112 havinga main drive switch 114 disposed thereon. The switch 114 may includefirst and second switches 114 a and 114 b formed together as a toggleswitch. The handle portion 112, which defines a handle axis H-H, isconfigured to be grasped by fingers of a user. The handle portion 112has an ergonomic shape providing ample palm grip leverage which helpsprevent the handle portion 112 from being squeezed out of the user'shand during operation. Each switch 114 a and 114 b is shown as beingdisposed at a suitable location on handle portion 112 to facilitate itsdepression by a user's finger or fingers.

Additionally, and with reference to FIGS. 1 and 2, switches 114 a, 114 bmay be used for starting and/or stopping movement of drive motor 200(FIG. 4). In one embodiment, the switch 114 a is configured to activatethe drive motor 200 in a first direction to advance firing rod (notexplicitly shown) in a distal direction thereby approximating the anviland the cartridge assemblies 162 and 164. Conversely, the switch 114 bmay be configured to retract the firing rod to open the anvil andcartridge assemblies 162 and 164 by activating the drive motor 200 in areverse direction. The retraction mode initiates a mechanical lock out,preventing further progression of stapling and cutting by the loadingunit 169. The toggle has a first position for activating switch 114 a, asecond position for activating switch 114 b, and a neutral positionbetween the first and second positions.

The housing 110, in particular the handle portion 112, includes switchshields 117 a and 117 b. The switch shields 117 a and 117 b may have arib-like shape surrounding the bottom portion of the switch 114 a andthe top portion of the switch 114 b, respectively. The switch shield 117a and 117 b prevent accidental activation of the switch 114. Further,the switches 114 a and 114 b have high tactile feedback requiringincreased pressure for activation.

In one embodiment, the switches 114 a and 114 b are configured asmulti-speed (e.g., two or more), incremental or variable speed switcheswhich control the speed of the drive motor 200 and the firing rod in anon-linear manner. For example, switches 114 a, 114 b can bepressure-sensitive. This type of control interface allows for gradualincrease in the rate of speed of the drive components from a slower andmore precise mode to a faster operation. To prevent accidentalactivation of retraction, the switch 114 b may be disconnectedelectronically until a fail safe switch 114 c is pressed.

The switches 114 a and 114 b are coupled to a non-linear speed controlcircuit which can be implemented as a voltage regulation circuit, avariable resistance circuit, or a microelectronic pulse width modulationcircuit. The switches 114 a and 144 b may interface with the controlcircuit by displacing or actuating variable control devices, such asrheostatic devices, multiple position switch circuit, linear and/orrotary variable displacement transducers, linear and/or rotarypotentiometers, optical encoders, ferromagnetic sensors, and Hall Effectsensors. This allows the switches 114 a and 114 b to operate the drivemotor 200 in multiple speed modes, such as gradually increasing thespeed of the drive motor 200 either incrementally or gradually dependingon the type of the control circuit being used, based on the depressionof the switches 114 a and 114 b.

FIGS. 2-4 illustrate an articulation mechanism 170, including anarticulation housing 172, a powered articulation switch 174, anarticulation motor 132 and a manual articulation knob 176. Translationof the powered articulation switch 174 activates the articulation motor132 which then actuates an articulation gear 233 of the articulationmechanism 170 as shown in FIG. 4. Pivoting of the manual articulationknob 176 bypasses the articulation motor 132 to actuate the articulationmechanism 170. The manual articulation knob 176 also provides anindication of the angulation of the end effector 160 with respect tolongitudinal axis A-A. Actuation of articulation mechanism 170 causesthe end effector 160 to move from its first position, where longitudinalaxis B-B is substantially aligned with longitudinal axis A-A, towards aposition in which longitudinal axis B-B is disposed at an angle tolongitudinal axis A-A. The powered articulation switch 174 may alsoincorporate similar non-linear speed controls as the clamping mechanism.These can be controlled by the switches 114 a and 114 b.

With reference to FIGS. 2 and 3, the housing 110 includes switch shields169 having a wing-like shape and extending from the top surface of thehousing 110 over the switch 174. The switch shields 169 preventaccidental activation of the switch 174 and require the user to reachbelow the shield 169 in order to activate the articulation mechanism170.

Additionally, articulation housing 172 and manual articulation knob 176are mounted to a rotating housing assembly 180. Rotation of a rotationknob 182 about first longitudinal axis A-A causes housing assembly 180as well as articulation housing 172 and manual articulation knob 176 torotate about first longitudinal axis A-A, and thus causes correspondingrotation of distal portion 224 of firing rod 220 and end effector 160about first longitudinal axis A-A. The articulation mechanism 170 iselectro-mechanically coupled to one or more conductive rings that aredisposed on a housing nose assembly 155 (FIG. 4). The conductive ringsmay be soldered and/or crimped onto the nose assembly 155 and are inelectrical contact with a power source 300 thereby providing electricalpower to the articulation mechanism 170. The nose assembly 155 may bemodular and may be attached to the housing 110 during assembly to allowfor easier soldering and/or crimping of the rings. The articulationmechanism 170 may include one or more brush and/or spring loadedcontacts in contact with the conductive rings such that as the housingassembly 180 is rotated along with the articulation housing 172 thearticulation mechanism 170 is in continuous contact with the conductiverings thereby receiving electrical power from the power source 300.

Further details of articulation housing 172, powered articulation switch174, manual articulation knob 176 and providing articulation to endeffector 160 are described in detail in commonly-owned U.S. patentapplication Ser. No. 11/724,733 filed Mar. 15, 2007, the contents ofwhich are hereby incorporated by reference in their entirety. It isenvisioned that any combinations of limit switches, proximity sensors(e.g., optical and/or ferromagnetic), linear variable displacementtransducers and shaft encoders which may be disposed within housing 110,may be utilized to control and/or record an articulation angle of endeffector 160 and/or position of the firing rod 220.

As shown in FIG. 4, the instrument 10 also includes a microcontroller400 electrically coupled to the motor 200 and various sensors disposedin the instrument 10. The sensors detect various operating parameters ofthe instrument 10 (e.g., linear speed, rotation speed, articulationposition, temperature, battery charge, and the like), which are thenreported to the microcontroller 400. The microcontroller 400 may thenrespond accordingly to the measured operating parameters (e.g., adjustthe speed of the motor 200, control articulation angle, shut-off thepower supply, report error conditions, etc.).

With continued reference to FIG. 4, a load switch 230 is disposed withinthe articulation housing 172. The switch 230 is connected in series withthe switch 114, preventing activation of the instrument 10 unless theloading unit 169 is properly loaded into the instrument 10. If theloading unit 169 is not loaded into the instrument 10, the main powerswitch (e.g., switch 114) is open, thereby preventing use of anyelectronic or electric components of the instrument 10. This alsoprevents any possible current draw from the power source 300 allowingthe power source 300 to maintain a maximum potential over its specifiedshelf life.

Thus, the switch 230 acts as a so-called “lock-out” switch whichprevents false activation of the instrument 10 since the switch 230 isinaccessible to external manipulation and can only be activated by theinsertion of the loading unit 169. The switch 230 is activated bydisplacement of a plunger or sensor tube 360 as the loading unit 169 isinserted into the endoscopic portion 140. Once the switch 230 isactivated, the power from the power source 300 is supplied to theelectronic components (e.g., sensors, microcontroller 400, etc.) of theinstrument 10 providing the user with access to a user interface andother inputs/outputs.

As shown in FIGS. 5-7, the endoscopic portion 140 includes the sensortube 360 (FIG. 6) therein disposed around the firing rod 220. The firingrod 220 passes through an opening 368 at a distal end of a sensor cap364 (FIG. 7). The sensor cap 364 includes a spring 365 and abuts theswitch 230. The sensor cap 364 is biased against the sensor tube 360,which is in contact with the distal end of the sensor cap 364.

As shown in FIGS. 5 and 6, when the loading unit 169 is loaded into theendoscopic portion 140, the proximal portion 171 abuts the sensor tube360, which displaces the sensor tube 360 in a proximal direction. Withreference to FIG. 7, the sensor tube 360 then pushes on the sensor cap364 in the proximal direction, which then compresses the spring 365 andactivates the switch 230 denoting that the loading unit 169 has beenproperly inserted.

Once the loading unit 169 is inserted into the endoscopic portion, theswitch 230 also determines whether the loading unit 169 is loadedcorrectly based on the position thereof. If the loading unit 169 isimproperly loaded, the switch 114 is not activated and an error code isrelayed to the user.

In another embodiment, the switch 230 may be adapted to sense the typeof a disposable loading unit 169 (e.g., articulating vs.non-articulating) engaged with the endoscopic portion 140. When anon-articulating loading unit is used, the sensor tube 360 is notengaged and the sensor cap 364 does not activate the switch 230. Theswitch 230 may still allow for operation of the instrument 10, butprevent operation of the articulation mechanism 170. When anarticulating loading unit 169 is used, the sensor tube 360 is engagedand the sensor cap 364 activates the switch 230. The switch 230 allowsfor operating of the instrument 10 including the articulation mechanism170. The articulating and non-articulating loading units may bedistinguished by a protrusion 173 (FIG. 5) or extended insertion tip(not explicitly shown) that when present, is configured to engage thesensor tube 360. In other words, non-articulating loading units do nothave a protrusion 173 for engaging the sensor tube 360 and thus do notactivate the switch 230, whereas the articulating loading units 169include the protrusion 173 and can thus enable operation of thearticulation mechanism 169. Thus, the sensor tube 360 is movable to afirst position or is not moved at all in response to engagement with anon-articulating loading unit and is movable to a second position inresponse to engagement of an articulating loading unit 169, in responseto which sensor tube 360 actuates the switch 230. The switch 230 iscoupled to the microcontroller 400 and is configured to transmit thesensor signal reflective of the sensor tube 360 being engaged by thearticulating loading unit 169. The microcontroller 400 then determinesthat the loading unit 169 is articulating and activates the articulationmechanism 170. Another type of sensing mechanism is described in acommonly-owned U.S. Pat. No. 5,865,361 entitled “Surgical StaplingApparatus” the contents of which are hereby incorporated herein in theirentirety by reference.

With reference to FIG. 6, the instrument 10 may also include a variableloading unit sensor 370. The loading unit sensor 370 includes a linearpotentiometer 290 disposed within the endoscopic portion 140. The linearpotentiometer 290 is electrically coupled to a contact 292 disposed onthe sensor tube 360. As the loading unit 169 is inserted into theendoscopic portion 140, the sensor tube 360 is moved in the proximaldirection. As a result of the movement of the sensor tube 360, thecontact 292 slides along the surface of the linear potentiometer 290.

In another embodiment shown in FIG. 8, the variable loading unit sensor370 may also include a linear variable differential transducer (LVDT)291 disposed about the sensor tube 360. The LVDT 291 includes atransformer 293 having three solenoidal coils arranged about the sensortube 360, with a center coil 295 being the primary, and the outer coils296 and 297 being the secondaries. A cylindrical ferromagnetic core 299may be attached to the sensor tube 360. To measure the displacement ofthe sensor tube 360, an alternating current is driven through the centercoil 295, causing a voltage to be induced in each secondaryproportional. As the sensor tube 360 moves, these mutual inductanceschange due to the shift in the magnetic field brought about by themagnetic core 299 causing the voltages induced in the outer coils 296and 297 to change. The coils 295, 296 and 297 may be connected inreverse series, so that the output voltage is the difference between thetwo voltages of the outer coils 296 and 297. When the core 299 is in itscentral position (e.g., equidistant between the outer coils 296 and 297)equal but opposite voltages are induced in outer coils 296 and 297, sothe output voltage is zero.

The variable loading unit sensor 370 is coupled to the microcontroller400, which is configured to determine the type of the loading unit 169coupled to the instrument 10 based on the signal from the variableloading unit sensor 370. If the sensor tube 360 is not engaged, such aswhen the loading unit 169 is not properly inserted, then the variableloading unit sensor 370 is not actuated and the microcontroller 400 doesnot activate the instrument 10. It is envisioned that various types ofloading units 169 may include protrusion 173 and/or extended insertiontips for engaging the sensor tube 360. A non-articulating loading unitmay include a protrusion 173 of a first type, while an articulatingloading unit 169 may have a protrusion 173 of a second type that is ofdifferent dimensions that the first type protrusion 173. In other words,the protrusion 173 of one loading unit 169 is either longer or shorterthan the protrusion 173 on another type of loading unit 169. As aresult, when inserted, each type of the loading unit 169 engages thesensor tube 360 by a predetermined distance. As a result, the variableloading unit sensor 370 then transmits the corresponding sensor signalcorresponding to the displacement of the sensor tube 360 to themicroprocessor 400, which then determines the type of the loading unit169 based thereon. The microcontroller 400 may then activate thearticulation mechanism 170 when the loading unit 169 is of articulatingtype.

The microcontroller 400 may then adjust operating parameters of theinstrument 10 to match the inserted loading unit 169 based on thedisplacement of the sensor tube 360. The adjustable parameters mayinclude firing stroke length, firing speed, degree of articulation andthe like. As discussed above, the microcontroller may also preventactuation of the instrument 10 until the loading unit 169 was loadedinto the instrument 10. In another embodiment, the variable loading unitsensor 370 may be disposed along any of the moving sensor parts, such asthe sensor tube 360 and the sensor cap 364.

It will be understood that various modifications may be made to theembodiments shown herein. Therefore, the above description should not beconstrued as limiting, but merely as exemplifications of preferredembodiments. Although specific features of the powered surgicalinstrument are shown in some of the drawings and not in others, this isfor convenience only as each feature may be combined with any or all ofthe other features in accordance with the aspects of the presentdisclosure. Other embodiments will occur to those skilled in the art andare within the following claims.

1. A surgical instrument, comprising: a handle portion; a body portionextending distally from the handle portion and defining a firstlongitudinal axis; a loading unit, the loading unit including a toolassembly, the loading adapted to be coupled to the body portion; asensor tube movably positioned within the body portion, the sensor tubeadapted to engage the loading unit; and a load switch coupled to amicrocontroller, wherein the load switch is adapted to be actuated bythe sensor tube when the sensor tube is engaged by the loading unitbeing inserted into the body portion.
 2. A surgical instrument accordingto claim 1, wherein upon actuation, the load switch signals themicroprocessor to activate the surgical instrument.
 3. A surgicalinstrument according to claim 1, wherein the sensor tube may only beengaged by a loading unit including an articulating tool assembly.
 4. Asurgical instrument according to claim 3, further comprising: anarticulation mechanism configured to articulate the articulating toolassembly.
 5. A surgical instrument according to claim 4, wherein uponengagement by the loading unit including the articulating tool assembly,the sensor tube actuates the load switch, which enables the articulationmechanism.
 6. A surgical instrument, comprising: a handle portion; abody portion extending distally from the handle portion and defining afirst longitudinal axis, the body portion having a distal end adapted toreleasably engage both articulating and non-articulating loading unittypes; an articulation mechanism configured to articulate anarticulating tool assembly coupled to an articulating loading unit; asensor tube movably positioned within the body portion, the sensor tubeadapted to engage the articulating loading unit; and a load switchcoupled to a microcontroller and adapted to be actuated by the sensortube when the sensor tube is engaged by the articulating loading unit,wherein upon actuation, the load switch signals the microprocessor toactivate the articulation mechanism.
 7. A surgical instrument accordingto claim 6, the sensing tube being movable to a first position inresponse to engagement of a non-articulating loading unit with the bodyportion and to a second position in response to engagement of thearticulating loading unit with the body portion.
 8. A surgicalinstrument according to claim 7, wherein movement of the sensing tube tothe second position engages the load switch.
 9. A surgical instrumentaccording to claim 7, wherein movement of the sensing tube to the firstposition signals the microprocessor to activate the surgical instrumentwithout the activation of the articulation mechanism.
 10. A surgicalinstrument, comprising: a handle portion; a body portion extendingdistally from the handle portion and defining a first longitudinal axis,the body portion having a distal end adapted to releasably engage aplurality of loading unit types; a sensor tube movably positioned withinthe body portion, the sensor tube adapted to engage each of theplurality of loading unit types and to move a predetermined distance inresponse thereto; and a variable loading unit sensor adapted todetermine a type of a loading unit engaged with the body portion basedon the predetermined distance the sensor tube has been displaced.
 11. Asurgical instrument according to claim 10, wherein the variable loadingunit sensor includes a potentiometer electrically coupled to a contactthat is coupled to the sensor tube, the potentiometer is configured tomeasure a sensor signal reflective the predetermined distance and totransmit the sensor signal to a microcontroller configured to determineda type of a loading unit engaged with the body portion based on thepredetermined distance the sensor tube has been displaced.
 12. Asurgical instrument according to claim 10, wherein the variable loadingunit sensor includes a linear variable differential transducer disposedabout the sensor tube, the linear variable differential transducerconfigured to measure a sensor signal reflective the predetermineddistance and to transmit the sensor signal to a microcontrollerconfigured to determine a type of a loading unit engaged with the bodyportion based on the predetermined distance the sensor tube has beendisplaced.
 13. A surgical instrument according to claim 10, furthercomprising: an articulation mechanism configured to articulate anarticulating tool assembly coupled to an articulating loading unit, thearticulating tool assembly defining a second longitudinal axis andhaving a proximal end, the articulating tool assembly being movable froma first position in which the second longitudinal axis is substantiallyaligned with the first longitudinal axis to at least a second positionin which the second longitudinal axis is disposed at an angle withrespect to the first longitudinal axis.
 14. A surgical instrumentaccording to claim 13, further comprising: a microcontroller coupled tothe variable loading unit sensor, wherein the microcontroller isconfigured to adjust at least one operating parameter of the instrumentbased on the type of a loading unit engaged with the body portion.
 15. Asurgical instrument according to claim 14, wherein the at least oneoperating parameter is selected from the group consisting of firingstroke length, firing speed and degree of articulation.
 16. A surgicalinstrument according to claim 14, wherein the microcontroller is furtherconfigured to activate the articulation mechanism when a loading unit isof articulating type.